A brake is one of the most important safety systems of a vehicle. Brakes are categorized into disk brakes and drum brakes according to techniques of causing friction. Most current vehicles use disk brakes that generate less heat and suffer less from deterioration in braking force attributed to thermal deformation of a brake, as compared to drum brakes.
A disc brake produces a braking force using friction created by hydraulic pressure-operated pads being pressed against one surface or both surfaces of a disk that rotates along with a wheel.
FIG. 1 is a cross-sectional view illustrating a conventional vehicle brake pad.
As illustrated in FIG. 1, the conventional vehicle brake pad includes a friction material layer 10 that directly creates friction and a back plate layer 40 that transfers pressure applied by a hydraulic cylinder.
The vehicle brake pad may further include an underlayer 20 interposed between the back plate layer 40 and the friction material layer 10 to reduce heat transfer to calipers or to improve a braking feel. The underlayer 20 is bonded to the back plate layer 40 via an adhesive layer 30.
The use of the underlayer 20 reduces raw material costs because the underlayer 20 is made of a material that is cheaper than the friction material layer 10.
The vehicle brake pad may additionally include a wear indicator 50 that measures and indicates the abrasion loss of the friction material layer 10 to reduce or prevent damage to the back plate layer 40 that is likely to occur when the friction material layer 10 is excessively lost beyond a critical amount due to abrasion, thereby resulting in direct contact between the back plate 40 and the disk. The wear indicator 50 may be attached to the back plate layer 40.
The conventional vehicle brake pad may additionally include a shim 60 that is disposed on a portion of the back plate layer 40 and is in direct contact with a hydraulic piston of a caliper, thereby improving noise, vibration, and harshness (NVH) characteristics. The shim 60 inhibits braking heat from being transferred to a cylinder and functions as a damper that reduces noise attributed to vibration.
The shim 60 is made of rubber or steel with a vibration damping ability and is attached to the back surface of the back plate layer 40. The shim 60 has limitations such that it has a thickness of 1 to 2 mm and is made of rubber or limited kinds of steel. The shim 60 can improve a vibration damping capacity at temperatures only within a very narrow specific temperature range. The vibration damping capacity dramatically deteriorates when the temperature is outside the specific temperature range, resulting in a deterioration of NVH characteristics.
The foregoing is intended merely to aid in the understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.